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Average Weather in December in Castries St. Lucia

In Castries, the month of December is characterized by essentially constant daily high temperatures, with daily highs around 84°F throughout the month, rarely exceeding 87°F or dropping below 82°F.

Daily low temperatures are around 76°F, rarely falling below 73°F or exceeding 79°F.

For reference, on September 2, the hottest day of the year, temperatures in Castries typically range from 78°F to 87°F, while on January 24, the coldest day of the year, they range from 75°F to 83°F.

Average High and Low Temperature in December

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in December

Average Hourly Temperature in December in Castries12 AM4 AM8 AM12 PM4 PM8 PM12 AM181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930303131NovJanwarmhot
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Clouds

The month of December in Castries experiences decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 54% to 42%.

The clearest day of the month is December 31, with clear, mostly clear, or partly cloudy conditions 58% of the time.

For reference, on September 27, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 71%, while on January 13, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 60%.

Cloud Cover in December

The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Castries, the chance of a wet day over the course of December is very rapidly decreasing, starting the month at 39% and ending it at 29%.

For reference, the year's highest daily chance of a wet day is 47% on November 9, and its lowest chance is 18% on March 3.

Probability of Precipitation in December

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during December in Castries is very rapidly decreasing, starting the month at 4.7 inches, when it rarely exceeds 8.6 inches or falls below 1.6 inches, and ending the month at 2.6 inches, when it rarely exceeds 5.7 inches or falls below 0.6 inches.

Average Monthly Rainfall in December

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

Over the course of December in Castries, the length of the day is essentially constant. The shortest day of the month is December 21, with 11 hours, 18 minutes of daylight and the longest day is December 1, with 11 hours, 22 minutes of daylight.

Hours of Daylight and Twilight in December

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Castries is 6:12 AM on December 1 and the latest sunrise is 15 minutes later at 6:27 AM on December 31.

The earliest sunset is 5:33 PM on December 1 and the latest sunset is 13 minutes later at 5:46 PM on December 31.

Daylight saving time is not observed in Castries during 2017.

For reference, on June 21, the longest day of the year, the Sun rises at 5:37 AM and sets 12 hours, 57 minutes later, at 6:34 PM, while on December 21, the shortest day of the year, it rises at 6:23 AM and sets 11 hours, 18 minutes later, at 5:41 PM.

Sunrise & Sunset with Twilight in December

The solar day over the course of December. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Castries is essentially constant during December, remaining around 100% throughout.

For reference, on April 30, the muggiest day of the year, there are muggy conditions 100% of the time, while on February 28, the least muggy day of the year, there are muggy conditions 96% of the time.

Humidity Comfort Levels in December

Humidity Comfort Levels in December in Castries0%10%20%30%40%50%60%70%80%90%100%181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930303131NovJanDec 1100%Dec 1100%Dec 3199%Dec 3199%Dec 11100%Dec 11100%Dec 2199%Dec 2199%miserablemiserableoppressiveoppressivemuggymuggyhumidhumid
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Castries is gradually increasing during December, increasing from 8.5 miles per hour to 9.3 miles per hour over the course of the month.

For reference, on June 22, the windiest day of the year, the daily average wind speed is 9.6 miles per hour, while on October 2, the calmest day of the year, the daily average wind speed is 7.0 miles per hour.

Average Wind Speed in December

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
The hourly average wind direction in Castries throughout December is predominantly from the east, with a peak proportion of 96% on December 26.

Wind Direction in December

The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Castries is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Castries is essentially constant during December, remaining within 1°F of 82°F throughout.

Average Water Temperature in December

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Castries is essentially constant during December, remaining within 0.1 kWh of 5.2 kWh throughout.

Average Daily Incident Shortwave Solar Energy in December

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Castries are 13.996 deg latitude, -61.006 deg longitude, and 43 ft elevation.

The topography within 2 miles of Castries contains very significant variations in elevation, with a maximum elevation change of 853 feet and an average elevation above sea level of 147 feet. Within 10 miles contains very significant variations in elevation (3,025 feet). Within 50 miles contains large variations in elevation (3,993 feet).

The area within 2 miles of Castries is covered by water (56%), trees (20%), and artificial surfaces (10%), within 10 miles by water (63%) and trees (26%), and within 50 miles by water (95%).

Data Sources

This report illustrates the typical weather in Castries year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Castries.

For each station, the records are corrected for the elevation difference between that station and Castries according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

The estimated value at Castries is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Castries and a given station.

The stations contributing to this reconstruction are: Hewanorra International Airport (79%, 28 kilometers, south) and Martinique Aimé Césaire International Airport (21%, 67 kilometers, north).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.